Was there a couple years ago. Didn't hike the trail but spent an entire day at the ruins. It's truly amazing. I believe the trail takes 3-4 days to hike. I think you should plan on an entire day at the ruins because there is a lot to see. Also be sure to give yourself some time to acclimatize. We had been in Lima, jumped on a plane to Cuzco and then took the train right up to the ruins. We had some altitude issues. Enjoy the trip.
Jeff